xl: allow to set the ratelimit value online for Credit2

Last part of the wiring necessary for allowing to
change the value of the ratelimit_us parameter online,
for Credit2 (like it is already for Credit1).

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

docs/man/xl.pod.1.in

@@ -1089,6 +1089,15 @@ to 65535 and the default is 256.
 
 Restrict output to domains in the specified cpupool.
 
+=item B<-s>, B<--schedparam>
+
+Specify to list or set pool-wide scheduler parameters.
+
+=item B<-r RLIMIT>, B<--ratelimit_us=RLIMIT>
+
+Attempts to limit the rate of context switching. It is basically the same
+as B<--ratelimit_us> in B<sched-credit>
+
 =back
 
 =item B<sched-rtds> [I<OPTIONS>]

tools/libxl/xl_cmdimpl.c

@@ -6457,8 +6457,29 @@ static int sched_credit_pool_output(uint32_t poolid)
     return 0;
 }
 
-static int sched_credit2_domain_output(
-    int domid)
+static int sched_credit2_params_set(int poolid,
+                                    libxl_sched_credit2_params *scinfo)
+{
+    if (libxl_sched_credit2_params_set(ctx, poolid, scinfo)) {
+        fprintf(stderr, "libxl_sched_credit2_params_set failed.\n");
+        return 1;
+    }
+
+    return 0;
+}
+
+static int sched_credit2_params_get(int poolid,
+                                    libxl_sched_credit2_params *scinfo)
+{
+    if (libxl_sched_credit2_params_get(ctx, poolid, scinfo)) {
+        fprintf(stderr, "libxl_sched_credit2_params_get failed.\n");
+        return 1;
+    }
+
+    return 0;
+}
+
+static int sched_credit2_domain_output(int domid)
 {
     char *domname;
     libxl_domain_sched_params scinfo;
@@ -6483,6 +6504,22 @@ static int sched_credit2_domain_output(
     return 0;
 }
 
+static int sched_credit2_pool_output(uint32_t poolid)
+{
+    libxl_sched_credit2_params scparam;
+    char *poolname = libxl_cpupoolid_to_name(ctx, poolid);
+
+    if (sched_credit2_params_get(poolid, &scparam))
+        printf("Cpupool %s: [sched params unavailable]\n", poolname);
+    else
+        printf("Cpupool %s: ratelimit=%dus\n",
+               poolname, scparam.ratelimit_us);
+
+    free(poolname);
+
+    return 0;
+}
+
 static int sched_rtds_domain_output(
     int domid)
 {
@@ -6582,17 +6619,6 @@ static int sched_rtds_pool_output(uint32_t poolid)
     return 0;
 }
 
-static int sched_default_pool_output(uint32_t poolid)
-{
-    char *poolname;
-
-    poolname = libxl_cpupoolid_to_name(ctx, poolid);
-    printf("Cpupool %s:\n",
-           poolname);
-    free(poolname);
-    return 0;
-}
-
 static int sched_domain_output(libxl_scheduler sched, int (*output)(int),
                                int (*pooloutput)(uint32_t), const char *cpupool)
 {
@@ -6838,17 +6864,22 @@ int main_sched_credit2(int argc, char **argv)
 {
     const char *dom = NULL;
     const char *cpupool = NULL;
+    int ratelimit = 0;
     int weight = 256;
+    bool opt_s = false;
+    bool opt_r = false;
     bool opt_w = false;
     int opt, rc;
     static struct option opts[] = {
         {"domain", 1, 0, 'd'},
         {"weight", 1, 0, 'w'},
+        {"schedparam", 0, 0, 's'},
+        {"ratelimit_us", 1, 0, 'r'},
         {"cpupool", 1, 0, 'p'},
         COMMON_LONG_OPTS
     };
 
-    SWITCH_FOREACH_OPT(opt, "d:w:p:", opts, "sched-credit2", 0) {
+    SWITCH_FOREACH_OPT(opt, "d:w:p:r:s", opts, "sched-credit2", 0) {
     case 'd':
         dom = optarg;
         break;
@@ -6856,6 +6887,13 @@ int main_sched_credit2(int argc, char **argv)
         weight = strtol(optarg, NULL, 10);
         opt_w = true;
         break;
+    case 's':
+        opt_s = true;
+        break;
+    case 'r':
+        ratelimit = strtol(optarg, NULL, 10);
+        opt_r = true;
+        break;
     case 'p':
         cpupool = optarg;
         break;
@@ -6871,10 +6909,31 @@ int main_sched_credit2(int argc, char **argv)
         return EXIT_FAILURE;
     }
 
-    if (!dom) { /* list all domain's credit scheduler info */
+    if (opt_s) {
+        libxl_sched_credit2_params scparam;
+        uint32_t poolid = 0;
+
+        if (cpupool) {
+            if (libxl_cpupool_qualifier_to_cpupoolid(ctx, cpupool,
+                                                     &poolid, NULL) ||
+                !libxl_cpupoolid_is_valid(ctx, poolid)) {
+                fprintf(stderr, "unknown cpupool \'%s\'\n", cpupool);
+                return EXIT_FAILURE;
+            }
+        }
+
+        if (!opt_r) { /* Output scheduling parameters */
+            if (sched_credit2_pool_output(poolid))
+                return EXIT_FAILURE;
+        } else {      /* Set scheduling parameters (so far, just ratelimit) */
+            scparam.ratelimit_us = ratelimit;
+            if (sched_credit2_params_set(poolid, &scparam))
+                return EXIT_FAILURE;
+        }
+    } else if (!dom) { /* list all domain's credit scheduler info */
         if (sched_domain_output(LIBXL_SCHEDULER_CREDIT2,
                                 sched_credit2_domain_output,
-                                sched_default_pool_output,
+                                sched_credit2_pool_output,
                                 cpupool))
             return EXIT_FAILURE;
     } else {

tools/libxl/xl_cmdtable.c

@@ -265,6 +265,8 @@ struct cmd_spec cmd_table[] = {
       "[-d <Domain> [-w[=WEIGHT]]] [-p CPUPOOL]",
       "-d DOMAIN, --domain=DOMAIN     Domain to modify\n"
       "-w WEIGHT, --weight=WEIGHT     Weight (int)\n"
+      "-s         --schedparam        Query / modify scheduler parameters\n"
+      "-r RLIMIT, --ratelimit_us=RLIMIT Set the scheduling rate limit, in microseconds\n"
       "-p CPUPOOL, --cpupool=CPUPOOL  Restrict output to CPUPOOL"
     },
     { "sched-rtds",